Removing phenols from gas liquor



' Sept. 20, 1932. w. TIDDY '1,878,979

REMOVING PHENOLS FROM GAS LIQUOR v Filed July zo, 192e VMI Nj l/melgy nwe ATTORNEYS '5j ammonia.

According to the-present invention, am-` moniacal gas liquor is rstsubjected to distillation to remove therefrom substantially Patented Sept. 20, 1932 Y SIGNMENTS, TO THE KOPPERS COMPANY F DELAWARE, OF PITTSBURGHL-PENN'-,

SYLVANIA, A CORPORATION 0F DELAWARE RnMovING rHENoLs rizoM'GAs LIQOR Application led July 20,

This invention relates to improvementsfin the elimination of phenols from ammoniacal gasliquors and comprises a process 1n which i the phenol is removed separately from the all of ythe free ammonia Which j the liquor` 1G' contains; the resultinghot gas liquor is then subjectedto scrubbing While at a tempera' ture of around 98 C. orhigher Withan inert gas to remove phenols from the liquors and theremaining liquor With its fixed arnmoniais then treated with lime and subjected to further distillation to set free the fixed ammonia and remove it therefrom.

In United States Patent No. 1,566,796 there N A F is described the removal of phenols fromam moniacal liquor'by passing the ammoniacal liquor through Va free ammonia still, then through va scrubber, and then through the vfixed ammonia still, With maintenance of a temperature around 98 C. or higher in the stills and scrubber and With passage of am-pA monia from the still through the scrubber to assist in the removal of Y phenol from the liquor. i f q f In the process of the present invention the ammoniacal liquor is rst` freed from free' ammonia With substantial completeness be-V` fore it is subjected .to scrubbing to remove the phenol therefrom, and the 'scrubbing visV carried out With substantial absence of free ammonia and with the circulation through the hot liquorof an inert gas such as steam, air or other'gases which are inert so far as the phenol is concerned. The phenol is therefore driven off in a form substantially'free Lfrom admixed ammonia and ammonium phenylate. The phenol vapors admixed vWith* the inertl gases are passed through an ab-` sorbent for the phenol such asa causticl soda 4Washer .maintained at a' high frtemperature and the inert gas freed from phenol can advantageously be returned to the scrubber in a cyclic'manner. 4By freeing thel ammoniacal liquor from free ammonia before it is subjected to scrubbing, and by 'employingran' inert gas for the scrubbing, the inert gas isA 192s. semi No. 294,236.

F rom the 'scrubberthe liquor from Whichkk the phenol has been removed but which still ycontains ixed ammonia is passed to the fixed ammonia! still Whereit is treated with lime and the fixed ammonia, decomposed and the resulting free ammonia removed and recovered. In the ordinary ammonia still the ammonia set free in the xed ammonia still entersthe bottom of the free ammonia still and passes upwardly therethrough, escaping admixed with theffreeammonia from the free ammonia still. 'In such case, however, the ammoniacal liquor drawn 0E `fromthe bottom ofthe free ammonia' still Will contain approximately the same content of free am` monia as the ammoniacal liquor entering the free ammonia stillgand, ifV such liquor Were passedtofthe scrubber, ammonia would be driven'oli' `vvithrthe phenol. This is avoided in the present process by freeing 'the liquorv With substantial completeness from free am monia before it passes to the scrubber;`r

'The' inventionvvill be further described in connection With the accompanying drawing,

which illustrates in a conventionaland diagrammatic manner an arrangement of appa-V for circulating the liquor fro'mthel free am-V monia still to the` scrubber and thence to the fixed ammonia still, together With means fori recovering phenols from 'the gases escaping from the scrubber. y

Referring first to Fig. l, the gasvliquor` enters throughk the gasv liquors inlet pipe l, to the distillation column or free ammonia still 2 Where all or substantially all ofthe freeammonia isv .drivenv of. This still is practice of the process 'of the invenfwww r f WILLIAM TIDDY, or' JEFFERsoNvILLE, PENNSYLVANIA, AssIGNoR, :BY MESNE dus heated by theintroduction of live steam Vat 3. The ammonia escapes in gaseous form through the outlet pipel. During its pas-V countercurrent flow of stear'n', air or other-in ertV gases or mixtures thereof entering through the pipe 8 in sufficient quantity to lremove the phenolic compounds fromkthe Y gas liquor with substantial completionor to Athe desired extent. Theinert vgases.carrying.

the phenol vapors escape through the outlet pipe 9.' The Aliquor leaving'thel scrubber 7( passes by means of thepipe 1U and pump 11 to the top of the lime leg 12 where itis treated with lime and the fixed ammonium salts are decomposed,'the liquor then flowing through theconnection 13 to the fixed ammonia lstill 14 in which the liquoris further heated and fromnwhich the last of the ammonia is drivenI as to maintainV it at a highfteinperaturepar-4 `ticularly where steam is employed as the in ammonia still 2 connects. from the free ammonia still', the lime :leg and-V off. Outlet pipes for the lammonia from the Y lime leg and fixed ammonia still are shown at 15 and 16,-and lead to thejsameoutlet pipe 17 Y with which the ammonia pipe 4 yfrom-the free the fixed ammonia still is thus taken offseparately and the v'apkors'theni combined.; The

ammonia gas from the lime leg and the fixed l..

ammonia stillV do not, as in` present day prac-A tice,` pass to thebottom of the free ammonia still.y Accordingly, thel liquor leavingthe bottom of thejfree ammonia still and going to the scrubber 7 will be free or si'ibstantiallyY so fromfr'ee ammonia but it will contain the normal content of fixed ammonia.` n Y The inert gases containing phenol vapors removed from the'gas liquor in the scrubber pass through the: outlet pipe Qtothebottom of a countercurrent insulated phenolabsorbent 18 wherethe phenol is recovered while allowing the inert gases practically `freedfrom phenol to escape lthrough -theoutlet pipe y19 andto be recirculated through the scrubbers for treatment of the additional gas liquor. A fan'20 located in the pipe 19 keeps ,the inert gases in circulation. VAl gas pipe' 21 permits additional inert gas to be introduced and a vent pipe' 2-2 permits any excess pressure in the system to be relieved. The phenol absorber may contain a strongtsolution of causticsoda'with steam coils for heating` so ert` gas. .The scrubber 7, phenol absorber 18 and ally connecting pipingare heat insulatedA to maintain a high temperatureofthe liquor and absorbing; liquid. The temperature is maintained throughout the circulating system so that noappreciable condensation-takes place,V thus ymaking itpossible to have ai continuous cycle of steam, air;` orotherinert The ammonia as inpresent day construction, but-an -imperforate partition 30 is interposed between `the free ammonia stillf'andfthe-lilme legv so that ammonia fromhthe lime leg and fixed ammonia still cannot pass up through the Y I liquor in the free ammonia still; and the lime leg and fixed ammonia still are provided with separate outlet pipes 15a and 16a ,for :the ammonia. In addition a steam' inlet 3a is soy provided atv the bottom ofthe free ammonia still 2ato insure heating and freeing of the liquor from its free ammonia.

he operation yof the apparatus of Fig. 2 is similar to that of Fig. 1. The gas liquor enters through the' gas liquor pipe 1a to the free ammonia still 2a and is heatedtherein by the introduction of live steam directly. intojthelliquor through the line 3a. The freev ammonia is driven outof the liquorwith substantial completeness so that the liquor passing through the line 5a to the scrubberV 7 a has been freediwith substantial completion from free ammonia.- After the removal of phenols in the scrubber 7atheliquor returns through the line 10a to the lime leg 12a and thexed ammonia still 14a, where the fixed, ammonia is set freeand separately taken off through iii separate Voutlet connectionsV without being tureris'required for effective driving off of Vphenol by the inert gases employed.

T he phenol is Vthusl driven ofi separatelyvfromthe ammonia and vice versa;v and f. in particular the phenol-isdriven off 'man am,

monia-free state from liquor which hasbeen Y' freed'fromfree ammonia but which still con-1 tainscombined ammonia; This'removal of phenols before the removal of combined amf` `moniahas the kimportant advantage that the .wasteV liquor :leavingthe still through the@ outlets23 and 23a fis substantially` freed from phenolsjwhere the phenols are completely removed by thel scrubbing operation. When phenols are present in the liquor in the fixed ammonia still they combine withlime to form calcium phenylate which is difiicult to'v remove. Y. .c

tion provides for the separate and independent removal and recovery from gas liquor of ammonia which may be substantially free from phenols and of phenol substantially, free from ammonia; and that the phenol removal step follows the removel of free ammonia with substantial completeness and pre- Y cedes the removal of xed ammonia, while n returning the liquorl after the removal of the free ammonia andfixed ammonia are separately taken off from the free and fixed ammonia stills. f

In order to prevent the presence of free am-v monia in the circulating inert gas of the phenol removal and recovery system, and the building up of ammonia in the system, it is important that the free ammonia still should be operated to -accomplish substantially complete distillation of free ammonia Yfrom the liquor and that the ammonia vfrom the lime leg and fixed ammonia still be taken off separately and not permitted to pass upwardly through the liquor in the free'ammonia still as in present day practice. v

I claim:

l. The improvement in the treatment of ammoniacal gas liquor, which comprises subjecting the same to distillation to remove free ammoniaA therefrom with substantial completeness, passing'the resulting liquor from which free ammonia has beensubstantially completely removed while at a temperature around 98 C. or higher to ascrubber and passing an ammonia free gas through the hot liquor to remove phenols from the liquor,

phenols to a fixed ammonia still and there treating it with lime to set free the fixed ammonia, and recovering the ammonia so set free.

2. The improvement in the treatment of ammoniacal gas liquor, which comprises subjecting the liquor to distillation and introducing steam directly into such liquor to effect substantially complete removal of free ammonia therefrom, passing the resultant liquor while at a temperature around 98 or higher to a scrubber and maintaining it at such temperature therein while passing ammonia-free gas counter-current thereto to remove phenols therefrom, passing the resulting liquor, after the removal of phenols, to aseparate ammonia still and treating the same` with lime to set free fixed ammonia, and

separately withdrawing such ammonia.

3. The improvement in Vthevtreatment of ammoniacal gas liquor, which comprises subjecting the same to distillation in a free *l ammonia still with steam to substantially completely remove free amoniaV therefrom, passing the resulting ammonia-free liquor While at a. temperature around 98 C. or higher to a scrubber and passing ammoniafree gas through the hot liquor -to remove phenols from the liquor, treating the thereby dephenolized liquor with lime to set free the fixed ammonia, distilling the limed liquor with s-team in a fixed ammonia still to remove the ammonia .thus set free, and by-passing` the ammonia vapors from said xed ammonia still around said free ammonia still.

4. The improvement in the process of treating ammoniacal gas liquor, which, when carried out in apparatus comprising a free ammonia still, a scrubber, a lime leg and a fixed ammonia still, comprises passing said liquor through said free still in ycountercurrent toa fiow ofsteam for the substantially complete removal of free ammonia therefrom, then treating the thus' distilled liquor at a temperature around 98 C. or higher in said scrubber with a current of substantially inert gas to remove phenol therefrom, then treatingthe liquor ,from which free ammonia and phenol have been removed in said lime leg for the conversion of ammonia originally present in fixed form to free ammonia, then passing the limed liquor through the fixed still in countercurrent to a flow of steamvfor the remo-val of ammonia originally present in fixed form, removing the ammoniacal vapors liberated in said fixed still and commingling them with ammonia-cal vasoA pors produced in said free still at a point re- `carried out in'apparatus comprising a free ammonia still, a scrubber, a lime leg and a fixed ammonia still, comprises passing said liquor through said free still in countercurrent to a flow of steam for the substantially complete removal of free ammonia therefrom, then treating the thus distilled liquor at a temperature around 98 C. or higher in said scrubber with a current of substantially inert gas to remove phenol therefrom, then treating the liquor from which' free ammonia and phenol have been removed in said lime leg for the conversion of ammonia originally present in fixed fo-rm to free ammonia, then passing the limed liquor through the xed still in countercurrent toa flow of steam for the removal of ammonia originally present in fixed form, and separately removing ammoniacal vapors liberated in said free still and in said fixed still.

In testimonyk whereof I affix my signature.

` WILLIAM TIDDY.

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